Related Field
The present invention relates to a reel-up for winding a paper web into a roll and to a method of winding a paper web to form a roll.
Description of Related Art
In a paper making machine, the ready-dried web is brought to a reel-up and wound on a reel spool to a roll of paper. This is often made in a Pope-type reel-up in which the paper web rests on and is driven by a supporting cylinder whose peripheral speed is equal to that of the paper web. Examples of such a Pope-type reel-up are disclosed in, for example, U.S. Pat. Nos. 3,743,199 and 5,251,835. In such reel-ups, the paper roll forms a nip with the supporting cylinder and a load is applied in the nip. In order to ensure that the paper roll being formed is substantially uniform, the nip pressure should be controlled. When nip pressure cannot be sufficiently controlled, this may result in paper rolls in which the paper has not been uniformly wound. This may also affect the paper properties. Especially tissue paper webs may be particularly sensitive to this problem.
To ensure a uniform winding, it has been suggested in for example U.S. Pat. No. 5,901,918 that the supporting cylinder be replaced by a flexible member such as a belt such that the paper web is engaged by the flexible member against the reel spool during winding.
In a reel-up of the kind disclosed in U.S. Pat. No. 5,901,918, i.e. a reel-up in which a flexible member such as a belt is used, it is of importance that the paper web adheres properly to the belt such that it does not become destabilized which could lead to wandering or wrinkles in the web. At the same time, the web should not adhere too strongly to the belt since that could lead to difficulties in transferring the paper web to the reel spool. To ensure a proper degree of adherence of the web to the belt, it has been suggested in U.S. Pat. No. 7,398,943 that the static electricity of at least one of the belt and the paper web be measured by a static measurement probe and that at least one static induction device be used. The static induction device should then be used for inducing a static charge into at least one of the endless flexible belt and the paper web. According to the '943 patent, the static charge difference between the web and the belt should be at least 6 kV or more in order to avoid poor web handling. However, the '943 patent also states that the static charge difference should be kept below 20 kV in order to avoid difficulties in connection with web transfer from the belt to the reel spool.
The object of the present invention is to provide a belt reel-up belt with improved control of the adherence of the paper web to the belt such that winding can be carried out in a controlled way.